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Journal articles on the topic 'Isotopic tracer'

Author: Grafiati

Published: 4 June 2021

Last updated: 1 February 2022

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1

Cobelli, C., G. Toffolo, D. M. Bier, and R. Nosadini. "Models to interpret kinetic data in stable isotope tracer studies." American Journal of Physiology-Endocrinology and Metabolism 253, no. 5 (1987): E551—E564. http://dx.doi.org/10.1152/ajpendo.1987.253.5.e551.

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In contrast to "weightless" radioactive tracers, stable isotope tracers have nonnegligible mass and are naturally present in the system, and the measured variable is a ratio of two isotopic species. These features do not allow stable isotopic tracer data analysis using straightforward analogy with radioactive tracer approaches, even though this practice is common. In this study, we present kinetic variables, models, and measurements for the analysis and interpretation of stable isotope tracer data. Assumptions and mathematical techniques for modeling the data when perturbation is both nonnegli

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2

Rosenblatt, J., and R. R. Wolfe. "Calculation of substrate flux using stable isotopes." American Journal of Physiology-Endocrinology and Metabolism 254, no. 4 (1988): E526—E531. http://dx.doi.org/10.1152/ajpendo.1988.254.4.e526.

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The use of stable isotope tracers to calculate substrate kinetics in humans is favored over the use of radioactive isotopes because of their greater safety and versatility. However, potential complications not met when dealing with radioactive tracers are caused by 1) the natural occurrence of the stable isotope used as a tracer and 2) the necessity to administer the tracer in an amount that cannot be treated as "massless." We therefore found it desirable to derive a theoretically valid equation for calculating the rate of appearance, Ra, of a substrate under steady-state conditions using a st

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3

Ala-aho, Pertti, Doerthe Tetzlaff, James P. McNamara, Hjalmar Laudon, and Chris Soulsby. "Using isotopes to constrain water flux and age estimates in snow-influenced catchments using the STARR (Spatially distributed Tracer-Aided Rainfall–Runoff) model." Hydrology and Earth System Sciences 21, no. 10 (2017): 5089–110. http://dx.doi.org/10.5194/hess-21-5089-2017.

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Abstract. Tracer-aided hydrological models are increasingly used to reveal fundamentals of runoff generation processes and water travel times in catchments. Modelling studies integrating stable water isotopes as tracers are mostly based in temperate and warm climates, leaving catchments with strong snow influences underrepresented in the literature. Such catchments are challenging, as the isotopic tracer signals in water entering the catchments as snowmelt are typically distorted from incoming precipitation due to fractionation processes in seasonal snowpack. We used the Spatially distributed

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van de Flierdt, Tina, Alexander M. Griffiths, Myriam Lambelet, Susan H. Little, Torben Stichel, and David J. Wilson. "Neodymium in the oceans: a global database, a regional comparison and implications for palaeoceanographic research." Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences 374, no. 2081 (2016): 20150293. http://dx.doi.org/10.1098/rsta.2015.0293.

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The neodymium (Nd) isotopic composition of seawater has been used extensively to reconstruct ocean circulation on a variety of time scales. However, dissolved neodymium concentrations and isotopes do not always behave conservatively, and quantitative deconvolution of this non-conservative component can be used to detect trace metal inputs and isotopic exchange at ocean–sediment interfaces. In order to facilitate such comparisons for historical datasets, we here provide an extended global database for Nd isotopes and concentrations in the context of hydrography and nutrients. Since 2010, combin

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Jahn, A., K. Lindsay, X. Giraud, et al. "Carbon isotopes in the ocean model of the Community Earth System Model (CESM1)." Geoscientific Model Development 8, no. 8 (2015): 2419–34. http://dx.doi.org/10.5194/gmd-8-2419-2015.

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Abstract. Carbon isotopes in the ocean are frequently used as paleoclimate proxies and as present-day geochemical ocean tracers. In order to allow a more direct comparison of climate model results with this large and currently underutilized data set, we added a carbon isotope module to the ocean model of the Community Earth System Model (CESM), containing the cycling of the stable isotope 13C and the radioactive isotope 14C. We implemented the 14C tracer in two ways: in the "abiotic" case, the 14C tracer is only subject to air–sea gas exchange, physical transport, and radioactive decay, while

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Jahn, A., K. Lindsay, X. Giraud, et al. "Carbon isotopes in the ocean model of the Community Earth System Model (CESM1)." Geoscientific Model Development Discussions 7, no. 6 (2014): 7461–503. http://dx.doi.org/10.5194/gmdd-7-7461-2014.

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Abstract. Carbon isotopes in the ocean are frequently used as paleo climate proxies and as present-day geochemical ocean tracers. In order to allow a more direct comparison of climate model results with this large and currently underutilized dataset, we added a carbon isotope module to the ocean model of the Community Earth System Model (CESM), containing the cycling of the stable isotope 13C and the radioactive isotope 14C. We implemented the 14C tracer in two ways: in the "abiotic" case, the 14C tracer is only subject to air–sea gas exchange, physical transport, and radioactive decay, while

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7

Hohl, Simon V., Shao-Yong Jiang, Sebastian Viehmann, et al. "Trace Metal and Cd Isotope Systematics of the Basal Datangpo Formation, Yangtze Platform (South China) Indicate Restrained (Bio)Geochemical Metal Cycling in Cryogenian Seawater." Geosciences 10, no. 1 (2020): 36. http://dx.doi.org/10.3390/geosciences10010036.

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The behaviour of bioavailable trace metals and their stable isotopes in the modern oceans is controlled by uptake into phototrophic organisms and adsorption on and incorporation into marine authigenic minerals. Among other bioessential metals, Cd and its stable isotopes have recently been used in carbonate lithologies as novel tracer for changes in the paleo primary productivity and (bio)geochemical cycling. However, many marine sediments that were deposited during geologically highly relevant episodes and which, thus, urgently require study for a better understanding of the paleo environment

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8

Mazariegos, Junior G., Jennifer C. Walker, Xiaomei Xu, and Claudia I. Czimczik. "Tracing Artificially Recharged Groundwater using Water and Carbon Isotopes." Radiocarbon 59, no. 2 (2016): 407–21. http://dx.doi.org/10.1017/rdc.2016.51.

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AbstractWe conducted an isotopic analysis of groundwater in Orange County, California, USA, around the Talbert Seawater Injection Barrier to determine if recycled water, used to artificially recharge local aquifers, carries a unique isotopic signature that can be used as a tracer. From September 2014 to April 2015, we collected groundwater from six privately owned wells within the coastal groundwater basin, along with various surface waters. All water samples were analyzed for their stable isotopic composition (δ18O, δD), the δ13C and 14C signature of the dissolved inorganic carbon (DIC) pool,

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Millard, Pierre, Baudoin Delépine, Matthieu Guionnet, Maud Heuillet, Floriant Bellvert, and Fabien Létisse. "IsoCor: isotope correction for high-resolution MS labeling experiments." Bioinformatics 35, no. 21 (2019): 4484–87. http://dx.doi.org/10.1093/bioinformatics/btz209.

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Abstract Summary Mass spectrometry (MS) is widely used for isotopic studies of metabolism and other (bio)chemical processes. Quantitative applications in systems and synthetic biology require to correct the raw MS data for the contribution of naturally occurring isotopes. Several tools are available to correct low-resolution MS data, and recent developments made substantial improvements by introducing resolution-dependent correction methods, hence opening the way to the correction of high-resolution MS (HRMS) data. Nevertheless, current HRMS correction methods partly fail to determine which is

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Emmanuel, S., J. A. Schuessler, J. Vinther, A. Matthews, and F. von Blanckenburg. "Iron isotope fractionation in marine invertebrates in near shore environments." Biogeosciences Discussions 11, no. 4 (2014): 5533–55. http://dx.doi.org/10.5194/bgd-11-5533-2014.

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Abstract. Chitons (Mollusca) are marine invertebrates that produce radula (teeth or rasping tongue) containing high concentrations of biomineralized magnetite and other iron bearing minerals. As Fe isotope signatures are influenced by redox processes and biological fractionation, Fe isotopes in chiton radula might be expected to provide an effective tracer of ambient oceanic conditions and biogeochemical cycling. Here, in a pilot study to measure Fe isotopes in marine invertebrates, we examine Fe isotopes in modern marine chiton radula collected from different locations in the Atlantic and Pac

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Emmanuel, S., J. A. Schuessler, J. Vinther, A. Matthews, and F. von Blanckenburg. "A preliminary study of iron isotope fractionation in marine invertebrates (chitons, Mollusca) in near-shore environments." Biogeosciences 11, no. 19 (2014): 5493–502. http://dx.doi.org/10.5194/bg-11-5493-2014.

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Abstract. Chitons (Mollusca) are marine invertebrates that produce radulae (teeth or rasping tongues) containing high concentrations of biomineralized magnetite and other iron-bearing minerals. As Fe isotope signatures are influenced by redox processes and biological fractionation, Fe isotopes in chiton radulae might be expected to provide an effective tracer of ambient oceanic conditions and biogeochemical cycling. Here, in a pilot study to measure Fe isotopes in marine invertebrates, we examine Fe isotopes in modern marine chiton radulae collected from different locations in the Atlantic and

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Hirave, Pranav, Guido L. B. Wiesenberg, Axel Birkholz, and Christine Alewell. "Understanding the effects of early degradation on isotopic tracers: implications for sediment source attribution using compound-specific isotope analysis (CSIA)." Biogeosciences 17, no. 8 (2020): 2169–80. http://dx.doi.org/10.5194/bg-17-2169-2020.

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Abstract. Application of compound-specific isotope analysis (CSIA) in sediment fingerprinting source apportionment studies is becoming more frequent, as it can potentially provide robust land-use-based source attribution of suspended sediments in freshwater and marine systems. Isotopic tracers such as δ13C values of vegetation-derived organic compounds are considered to be suitable for the CSIA-based fingerprinting method. However, a rigorous evaluation of tracer conservativeness in terms of the stability of isotopic signature during detachment and transport of soil during erosion is essential

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Piovano, Thea I., Doerthe Tetzlaff, Sean K. Carey, Nadine J. Shatilla, Aaron Smith, and Chris Soulsby. "Spatially distributed tracer-aided runoff modelling and dynamics of storage and water ages in a permafrost-influenced catchment." Hydrology and Earth System Sciences 23, no. 6 (2019): 2507–23. http://dx.doi.org/10.5194/hess-23-2507-2019.

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Abstract. Permafrost strongly controls hydrological processes in cold regions. Our understanding of how changes in seasonal and perennial frozen ground disposition and linked storage dynamics affect runoff generation processes remains limited. Storage dynamics and water redistribution are influenced by the seasonal variability and spatial heterogeneity of frozen ground, snow accumulation and melt. Stable isotopes are potentially useful for quantifying the dynamics of water sources, flow paths and ages, yet few studies have employed isotope data in permafrost-influenced catchments. Here, we app

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14

Li, Shilei, Weiqiang Li, Brian L. Beard, et al. "K isotopes as a tracer for continental weathering and geological K cycling." Proceedings of the National Academy of Sciences 116, no. 18 (2019): 8740–45. http://dx.doi.org/10.1073/pnas.1811282116.

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The causal effects among uplift, climate, and continental weathering cannot be fully addressed using presently available geochemical proxies. However, stable potassium (K) isotopes can potentially overcome the limitations of existing isotopic proxies. Here we report on a systematic investigation of K isotopes in dissolved load and sediments from major rivers and their tributaries in China, which have drainage basins with varied climate, lithology, and topography. Our results show that during silicate weathering, heavy K isotopes are preferentially partitioned into aqueous solutions. Moreover,

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15

Ulusoy, Ulvi, and John E. Whitley. "Profiles of faecal output of rare earth elements and stable isotopic tracers of iron and zinc after oral administration." British Journal of Nutrition 84, no. 5 (2000): 605–17. http://dx.doi.org/10.1017/s000711450000194x.

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The objectives of this study were to confirm the non-absorbability and the reproducibility of faecal excretion kinetics of orally administered rare earth elements, and to investigate the excretion profiles of rare earth elements and stable isotopic tracers of Fe and Zn to establish the extent to which rare earth element markers duplicate the behaviour of isotopic tracers. Two investigations were performed: (1) six healthy subjects consumed a solution containing five rare earth elements in amounts varying from 1 to 10 mg; (2) seven healthy subjects were given a standard solution labelled with S

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16

Kelleher, J. K., and T. M. Masterson. "Model equations for condensation biosynthesis using stable isotopes and radioisotopes." American Journal of Physiology-Endocrinology and Metabolism 262, no. 1 (1992): E118—E125. http://dx.doi.org/10.1152/ajpendo.1992.262.1.e118.

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Important syntheses in living systems occur by condensation reactions of the type nA----1B (where n is the number of A molecules needed to synthesize 1 molecule of B). Quantitative relationships for estimating the rate of synthesis of B from radioactive and stable isotope tracers are compared. With radioisotope tracers, only a single quantity is detected, the amount of radioactivity in B. In contrast, isotopes of varying mass produce multiple mass isotopomers B that are detected using mass spectrometry. The analysis demonstrates that the rate of synthesis of B is identifiable from stable isoto

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17

Roche, D. M. "δ<sup>18</sup>O water isotope in the <i>i</i>LOVECLIM model (version 1.0) – Part 1: Implementation and verification". Geoscientific Model Development 6, № 5 (2013): 1481–91. http://dx.doi.org/10.5194/gmd-6-1481-2013.

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Abstract. A new 18O stable water isotope scheme is developed for three components of the iLOVECLIM coupled climate model: atmospheric, oceanic and land surface. The equations required to reproduce the fractionation of stable water isotopes in the simplified atmospheric model ECBilt are developed consistently with the moisture scheme. Simplifications in the processes are made to account for the simplified vertical structure including only one moist layer. Implementation of these equations together with a passive tracer scheme for the ocean and a equilibrium fractionation scheme for the land sur

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Douglas, Peter M. J., Daniel A. Stolper, John M. Eiler, et al. "Methane clumped isotopes: Progress and potential for a new isotopic tracer." Organic Geochemistry 113 (November 2017): 262–82. http://dx.doi.org/10.1016/j.orggeochem.2017.07.016.

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19

Reedy, Brian J., James K. Beattie, and Richard T. Lowson. "Oxygen-18 Sulfate Isotopomers Monitored by Infrared Spectroscopy." Applied Spectroscopy 48, no. 6 (1994): 691–94. http://dx.doi.org/10.1366/000370294774368893.

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Infrared spectroscopy has been used with oxygen-18 isotopic tracer experiments to provide insight into the mechanism of formation of sulfate by the air oxidation of sulfite, thiosulfate, or tetrathionate ions. The relative amounts of each of the different isotope isomers, or isotopomers, can be observed qualitatively by their characteristic totally symmetric vibrational mode frequencies. The source of the 18O can be either dioxygen or the solvent water. By reversing the source of the isotope, one can check the results for isotopic exchange and/or impurities.

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20

Wang, Pei, Yujing Deng, and Zhongwang Wei. "Modeling Investigation of Diurnal Variations in Water Flux and Its Components with Stable Isotopic Tracers." Atmosphere 10, no. 7 (2019): 403. http://dx.doi.org/10.3390/atmos10070403.

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The isotopic compositions of water fluxes provide valuable insights into the hydrological cycle and are widely used to quantify biosphere–atmosphere exchange processes. However, the combination of water isotope approaches with water flux components remains challenging. The Iso-SPAC (coupled heat, water with isotopic tracer in soil–plant–atmosphere-continuum) model is a useful framework for simulating the dynamics of water flux and its components, and for coupling with isotopic fractionation and mixing processes. Here, we traced the isotopic fractionation processes with separate soil evaporatio

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21

Griffith, David W. T. "Calibration of isotopologue-specific optical trace gas analysers: a practical guide." Atmospheric Measurement Techniques 11, no. 11 (2018): 6189–201. http://dx.doi.org/10.5194/amt-11-6189-2018.

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Abstract. The isotopic composition of atmospheric trace gases such as CO2 and CH4 provides a valuable tracer for the sources and sinks that contribute to atmospheric trace gas budgets. In the past, isotopic composition has typically been measured with high precision and accuracy by isotope ratio mass spectrometry (IRMS) offline and separately from real-time or flask-based measurements of concentrations or mole fractions. In recent years, development of infrared optical spectroscopic techniques based on laser and Fourier-transform infrared spectroscopy (FTIR) has provided high-precision measure

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22

K. Dideriksen, J. A. Baker, and S. L. S. Stipp. "Fe isotope fractionation between inorganic aqueous Fe(III) and a Fe siderophore complex." Mineralogical Magazine 72, no. 1 (2008): 313–16. http://dx.doi.org/10.1180/minmag.2008.072.1.313.

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AbstractIn oxic waters, dissolved Fe exists dominantly as Fe(III) complexes with strongly coordinating, siderophore-like ligands. In this study, we have determined an equilibrium Fe isotope fractionation of 0.6% (∆56Fe) between inorganic Fe(III) and Fe(III) siderophore complexes using the siderophore desferrioxamine B as a model compound. The 57Fe tracer experiments show that the Fe isotopes ofthe siderophores exchange readily with dissolved inorganic Fe. The results indicate that organic ligands are likely to be important in the generation ofFe isotope signatures in oxic environments. For exa

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23

Heiling, V. J., J. M. Miles, and M. D. Jensen. "How valid are isotopic measurements of fatty acid oxidation?" American Journal of Physiology-Endocrinology and Metabolism 261, no. 5 (1991): E572—E577. http://dx.doi.org/10.1152/ajpendo.1991.261.5.e572.

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These studies were performed 1) to compare two isotopic methods (3H2O and 14CO2 production) of measuring free fatty acid (FFA) oxidation; 2) to determine whether isotopic estimates of fatty acid oxidation during hypoinsulinemia are plausible when compared with those obtained using indirect calorimetry; and 3) to examine whether the delay between the exit of [14C]FFA from plasma and the appearance of 14CO2 in breath is accounted for solely by bicarbonate kinetics. Studies in 11 healthy volunteers revealed that [14C]- and [3H]FFA tracers provide similar estimates of FFA turnover and oxidation. I

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Brkić, Željka, Mladen Kuhta, Tamara Hunjak, and Ozren Larva. "Regional Isotopic Signatures of Groundwater in Croatia." Water 12, no. 7 (2020): 1983. http://dx.doi.org/10.3390/w12071983.

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Tracer methods are useful for investigating groundwater travel times and recharge rates and analysing impacts on groundwater quality. The most frequently used tracers are stable isotopes and tritium. Stable isotopes of oxygen (δ18O) and hydrogen (δ2H) are mainly used as indicators of the recharge condition. Tritium (3H) is used to estimate an approximate mean groundwater age. This paper presents the results of an analysis of stable isotope data and tritium activity in Croatian groundwater samples that were collected between 1997 and 2014 at approximately 100 sites. The composition of the stabl

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He, Mao-Yong, Li Deng, Hai Lu, and Zhang-Dong Jin. "Elimination of the boron memory effect for rapid and accurate boron isotope analysis by MC-ICP-MS using NaF." Journal of Analytical Atomic Spectrometry 34, no. 5 (2019): 1026–32. http://dx.doi.org/10.1039/c9ja00007k.

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Boron isotope is a useful tracer for fluid–rock interactions and subduction processes, as well as a proxy for paleo-ocean pH. However, the strong B memory effect presents a great challenge in precisely measuring B isotopic ratios and accurately using MC-ICP-MS.

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Layman, D. K., and R. R. Wolfe. "Sample site selection for tracer studies applying a unidirectional circulatory approach." American Journal of Physiology-Endocrinology and Metabolism 253, no. 2 (1987): E173—E178. http://dx.doi.org/10.1152/ajpendo.1987.253.2.e173.

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The optimal arterial or venous sites for infusion and sampling during isotopic tracer studies have not been established. This study determined the relationship of plasma and tissue enrichment (E) when isotopes were infused in an artery and sampled from a vein (av mode) or infused in a vein and sampled from an artery (va mode). Adult dogs were given primed constant infusions of [3-13C]lactate, [1-13C]leucine, and 14C-labeled bicarbonate. Simultaneous samples were drawn from the vena cava, aortic arch, and breath. Tissue samples were removed from skeletal muscle, liver, kidney, and gut. Breath s

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Zhang, X. J., D. L. Chinkes, Y. Sakurai, and R. R. Wolfe. "An isotopic method for measurement of muscle protein fractional breakdown rate in vivo." American Journal of Physiology-Endocrinology and Metabolism 270, no. 5 (1996): E759—E767. http://dx.doi.org/10.1152/ajpendo.1996.270.5.e759.

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We have developed a novel method to measure the fractional breakdown rate (FBR) of muscle protein. This method involves infusing isotope tracer to reach an isotopic equilibrium and then observing its decay in the arterial blood and muscle intracellular pool. The calculation of FBR is based on the rate at which tracee released from breakdown dilutes the intracellular enrichment using a modified precursor-product equation. To test this method, L-[1,2-13C2]leucine and L-[ring-13C6]phenylalanine were infused into six dogs for measurement of FBR and fractional synthesis rate (FSR), respectively. Le

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Marchina, Chiara, Valeria Lencioni, Francesca Paoli, Marzia Rizzo, and Gianluca Bianchini. "Headwaters’ Isotopic Signature as a Tracer of Stream Origins and Climatic Anomalies: Evidence from the Italian Alps in Summer 2018." Water 12, no. 2 (2020): 390. http://dx.doi.org/10.3390/w12020390.

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Glaciers are shrinking due to global warming, resulting in a diminishing contribution of ice and snowmelt to headwaters and subsequent consequences to freshwater ecosystems. Within this context, we tested whether water-stable isotopes are spatio-temporal tracers of (i) water in high altitude periglacial environments, being the isotopic signature of surface water inherited from the snow/icemelt, groundwater, and rainfall; and (ii) regional (year-specific) meteorological conditions, being the isotopic signature of precipitations affected by air temperature, humidity and aqueous vapour origin, as

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Rosenblatt, J., D. Chinkes, M. Wolfe, and R. R. Wolfe. "Stable isotope tracer analysis by GC-MS, including quantification of isotopomer effects." American Journal of Physiology-Endocrinology and Metabolism 263, no. 3 (1992): E584—E596. http://dx.doi.org/10.1152/ajpendo.1992.263.3.e584.

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In metabolic tracer studies it is frequently useful to infuse tracers that are differently labeled variants of the same molecule. These tracers are known as isotopomers. Analysis of the enrichment of each isotopic analogue can be accomplished by gas chromatography-mass spectrometry (GC-MS). However, the raw GC-MS data must be corrected to give the information required. This paper addresses how to transform the raw GC-MS data, consisting of relative abundance ratios at specific ion masses, into relative molar ratios of tracer and tracee molecules. Several correction factors are necessary. First

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Wu, Li, Ling, et al. "Further Characterization of the RW-1 Monazite: A New Working Reference Material for Oxygen and Neodymium Isotopic Microanalysis." Minerals 9, no. 10 (2019): 583. http://dx.doi.org/10.3390/min9100583.

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The oxygen (O) and neodymium (Nd) isotopic composition of monazite provides an ideal tracer of metamorphism and hydrothermal activity. Calibration of the matrix effect and monitoring of the external precision of monazite O–Nd isotopes with microbeam techniques, such as secondary ion mass spectrometry (SIMS) and laser ablation-multicollector-inductively coupled plasma-mass spectrometry (LA-MC-ICPMS), require well-characterized natural monazite standards for precise microbeam measurements. However, the limited number of standards available is impeding the application of monazite O–Nd isotopes. H

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Adloff, Markus, Andy Ridgwell, Fanny M. Monteiro, et al. "Inclusion of a suite of weathering tracers in the cGENIE Earth system model – muffin release v.0.9.23." Geoscientific Model Development 14, no. 7 (2021): 4187–223. http://dx.doi.org/10.5194/gmd-14-4187-2021.

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Abstract. The metals strontium (Sr), lithium (Li), osmium (Os) and calcium (Ca), together with their isotopes, are important tracers of weathering and volcanism – primary processes which shape the long-term cycling of carbon and other biogeochemically important elements at the Earth's surface. Traditionally, because of their long residence times in the ocean, isotopic shifts in these four elements observed in the geologic record are almost exclusively interpreted with the aid of isotope-mixing, tracer-specific box models. However, such models may lack a mechanistic description of the links bet

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Crenn, Pascal, Francois Thuillier, Benjamin Rakatoambinina, Monique Rongier, Dominique Darmaun, and Bernard Messing. "Duodenal vs. gastric administration of labeled leucine for the study of splanchnic metabolism in humans." Journal of Applied Physiology 89, no. 2 (2000): 573–80. http://dx.doi.org/10.1152/jappl.2000.89.2.573.

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Low-rate (6 ml/h) intragastric infusion of stable, isotope-labeled amino acids is commonly used to assess the splanchnic handling of amino acids in humans. However, when used in the postabsorptive state, this method yields unreliable plasma isotopic enrichments, with a coefficient of variation >10%. In this metabolic condition, we confirmed in six subjects that an intragastric infusion of l-[2H3]leucine at 6 ml/h yields an unreliable isotopic steady state in plasma amino acids with a coefficient of variation of 43 ± 12% (mean ± SD). In five additional subjects, we assessed the effects of 1)

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Romijn, J. A., D. L. Chinkes, J. M. Schwarz, and R. R. Wolfe. "Lactate-pyruvate interconversion in blood: implications for in vivo tracer studies." American Journal of Physiology-Endocrinology and Metabolism 266, no. 3 (1994): E334—E340. http://dx.doi.org/10.1152/ajpendo.1994.266.3.e334.

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We have evaluated lactate and pyruvate kinetics in whole blood or plasma by the addition of [1-13C]lactate (n = 5) or [1-13C]pyruvate (n = 5) and application of compartmental modeling to the resulting data. Pyruvate and lactate concentrations and tracer-to-tracee ratios were measured at frequent intervals for 45 min. Pyruvate and lactate tracer-to-tracee ratios equilibrated almost completely within 3-4 min in whole blood, whereas there was no isotopic exchange in plasma. The average rate of interconversion between unlabeled lactate and pyruvate was four to five times (pyruvate to lactate) and

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Widory, David, Wolfram Kloppmann, Laurence Chery, Jacky Bonnin, Houda Rochdi, and Jean-Luc Guinamant. "Nitrate in groundwater: an isotopic multi-tracer approach." Journal of Contaminant Hydrology 72, no. 1-4 (2004): 165–88. http://dx.doi.org/10.1016/j.jconhyd.2003.10.010.

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Hungate, Bruce A., Rebecca L. Mau, Egbert Schwartz, et al. "Quantitative Microbial Ecology through Stable Isotope Probing." Applied and Environmental Microbiology 81, no. 21 (2015): 7570–81. http://dx.doi.org/10.1128/aem.02280-15.

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ABSTRACTBacteria grow and transform elements at different rates, and as yet, quantifying this variation in the environment is difficult. Determining isotope enrichment with fine taxonomic resolution after exposure to isotope tracers could help, but there are few suitable techniques. We propose a modification tostableisotopeprobing (SIP) that enables the isotopic composition of DNA from individual bacterial taxa after exposure to isotope tracers to be determined. In our modification, after isopycnic centrifugation, DNA is collected in multiple density fractions, and each fraction is sequenced s

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Herzka, Sharon Z., and G. Joan Holt. "Changes in isotopic composition of red drum (Sciaenops ocellatus) larvae in response to dietary shifts: potential applications to settlement studies." Canadian Journal of Fisheries and Aquatic Sciences 57, no. 1 (2000): 137–47. http://dx.doi.org/10.1139/f99-174.

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The stable isotope composition of larval fish tissues may serve as a chemical tracer of recent settlement due to food web differences among planktonic and demersal habitats. We present the background for the utilization of δ13C and δ15N to trace settlement of red drum (Sciaenops ocellatus), an estuarine-dependent species. The effect of ontogeny and temperature on the relative contribution of growth and metabolic turnover to changes in isotopic composition was examined by simulating dietary shifts in the laboratory. Fractionation was examined as a function of size and the effect of food depriva

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Lancellotti, Lisa, Simona Sighinolfi, Andrea Marchetti, and Lorenzo Tassi. "Use of Lead Isotopic Ratios as Geographical Tracer for Lambrusco PDO Wines." Molecules 25, no. 7 (2020): 1641. http://dx.doi.org/10.3390/molecules25071641.

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In this study, the lead isotope signature was tested with the aim to verify its potential as geographic tracer for wine production and particularly for the Lambrusco PDO wines of the province of Modena (Italy). A solid phase extraction procedure, for separating lead from the investigated matrices, soil and wine, was optimized. Furthermore, different mathematical models, based on an exponential law and internal or external correction approach, were evaluated for the correction of instrumental mass dependent fractionation. The optimized analytical procedure yielded isotopic ratio data relative t

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Banda, Limbikani C., Michael O. Rivett, Robert M. Kalin, et al. "Water–Isotope Capacity Building and Demonstration in a Developing World Context: Isotopic Baseline and Conceptualization of a Lake Malawi Catchment." Water 11, no. 12 (2019): 2600. http://dx.doi.org/10.3390/w11122600.

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Developing countries such as Malawi require improved access to isotope tracer tools to better characterize and manage water resources threatened by land development, deforestation and climate change. This is the first published study to use an isotope facility developed in Malawi for this purpose, instead of relying upon sample analyses from abroad. Results from this new facility are used to evaluate an important Lake Malawi catchment in the Rift Valley. This work successfully established a stable-isotope baseline, hydrochemical signatures, and system conceptualization against which future pol

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McLean, Noah M., Daniel J. Condon, Blair Schoene, and Samuel A. Bowring. "Evaluating uncertainties in the calibration of isotopic reference materials and multi-element isotopic tracers (EARTHTIME Tracer Calibration Part II)." Geochimica et Cosmochimica Acta 164 (September 2015): 481–501. http://dx.doi.org/10.1016/j.gca.2015.02.040.

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ACKER, Bernadette A. C. VAN, Karel W. E. HULSEWÉ, Anton J. M. WAGENMAKERS, et al. "Absence of glutamine isotopic steady state: implications for the assessment of whole-body glutamine production rate." Clinical Science 95, no. 3 (1998): 339–46. http://dx.doi.org/10.1042/cs0950339.

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1.During infusion of [5-15N]glutamine in patients with gastrointestinal cancer we unexpectedly observed a gradual decrease in time of the appearance rate (Ra) of glutamine in plasma. Here we investigate whether the failure to achieve a plateau isotopic enrichment in plasma is, among other factors, due to incomplete equilibration of the glutamine tracer with the large intramuscular free glutamine pool. 2.Plasma and intramuscular glutamine enrichment were measured during 6–11 ;h infusions of L-[5-15N]glutamine and L-[1-13C]glutamine in post-absorptive patients admitted to hospital for elective a

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Bishop, Kevin, and Etienne Dambrine. "Localization of tree water uptake in Scots pine and Norway spruce with hydroiogical tracers." Canadian Journal of Forest Research 25, no. 2 (1995): 286–97. http://dx.doi.org/10.1139/x95-033.

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This study explores the potential of hydroiogical tracers for determining the proportion of water uptake by Scots pine (Pinussylvestris L.) and Norway spruce (Piceaabies (L.) Karst.) from different layers in the upper 3 dm of podzolized forest soil. To improve the resolution of the tracer technique, a pair of tracers was employed. One tracer was the naturally occurring vertical gradient in the oxygen isotope ratio,δ18O, of soil solution. The second tracer was a 3H solution placed in the mor layer. A three-component mixing model of water uptake was used to simulate the content of these two trac

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Williams, B. D., I. Plag, J. Troup, and R. R. Wolfe. "Isotopic determination of glycolytic flux during intense exercise in humans." Journal of Applied Physiology 78, no. 2 (1995): 483–90. http://dx.doi.org/10.1152/jappl.1995.78.2.483.

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We used a new stable isotope tracer approach incorporating muscle intracellular lactate enrichment to determine the flux of glucose/glucosyl toward lactate [i.e., nonoxidized pyruvate (Pyr) production (Pyrno)] in moderately trained cyclists exercising at approximately 80% (259 +/- 16 W; n = 6) and approximately 100% (341 +/- 9 W; n = 8) maximal O2 uptake (VO2max). Primed constant infusions of [6,6-2H2]glucose and [13C]lactate or [13C]Pyr tracers were given, and rapid achievement of plateau was obtained during exercise by increasing the infusion rates at exercise onset to correspond with expect

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Wolfe, R. R., F. Jahoor, and H. Miyoshi. "Evaluation of the isotopic equilibration between lactate and pyruvate." American Journal of Physiology-Endocrinology and Metabolism 254, no. 4 (1988): E532—E535. http://dx.doi.org/10.1152/ajpendo.1988.254.4.e532.

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When an isotopic tracer is infused for the purpose of determining the rate of turnover or oxidation of a substrate, it is assumed that the resulting isotopic enrichment by the tracer will reflect the kinetics of only the pool of interest. However, this may not be the case when carbon-labeled lactate is infused, since rapid isotopic exchange with the intracellular pyruvate and alanine pools could potentially occur. Therefore we have determined the extent of isotopic exchange occurring during the infusion of [3-13C]lactate into six anesthetized dogs. In the steady state, pyruvate enrichment was

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Jensen, M. D., P. J. Rogers, M. G. Ellman, and J. M. Miles. "Choice of infusion-sampling mode for tracer studies of free fatty acid metabolism." American Journal of Physiology-Endocrinology and Metabolism 254, no. 5 (1988): E562—E565. http://dx.doi.org/10.1152/ajpendo.1988.254.5.e562.

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To determine the preferred infusion-sampling mode for isotopic studies of free fatty acid (FFA) metabolism, tracer [( 14C]palmitate) was infused into the left ventricle of five anesthetized dogs, and tracee ([3H]palmitate) was infused into three separate peripheral veins of each dog. The [14C]palmitate specific activity (SA) was lower in mixed venous than arterial blood, and [3H]palmitate SA was equal in both sites. The actual infusion rate of [3H]palmitate [2.15 +/- 0.31 X 10(5) disintegrations/min (dpm).kg-1.min-1] could be accurately predicted (2.14 +/- 0.32 X 10(5) dpm.kg-1.min-1) using th

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Arienzo, Ilenia, Marcello Liotta, Lorenzo Brusca, Massimo D’Antonio, Federica Lupone, and Ciro Cucciniello. "Analytical Method for Lithium Isotopes Determination by Thermal Ionization Mass Spectrometry: A Useful Tool for Hydrogeochemical Applications." Water 12, no. 8 (2020): 2182. http://dx.doi.org/10.3390/w12082182.

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The low temperature realm such as the geothermal systems, characterized by a large variety of near-Earth surface processes, has been the object of several isotopic studies, some of them including lithium isotopes. However, much work can still be done to systematically use lithium as tracer of geochemical processes in deep and shallow Earth reservoirs. A pilot study has been performed for the determination of lithium-isotope ratio by thermal ionization mass spectrometry (TIMS), a technique poorly employed with respect to other methods such as inductively coupled plasma mass spectrometry, being

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Holm, Lars, Søren Reitelseder, Kasper Dideriksen, Rie H. Nielsen, Jacob Bülow, and Michael Kjaer. "The single-biopsy approach in determining protein synthesis in human slow-turning-over tissue: use of flood-primed, continuous infusion of amino acid tracers." American Journal of Physiology-Endocrinology and Metabolism 306, no. 11 (2014): E1330—E1339. http://dx.doi.org/10.1152/ajpendo.00084.2014.

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Muscle protein synthesis (MPS) rate is determined conventionally by obtaining two or more tissue biopsies during a primed, continuous infusion of a stable isotopically labeled amino acid. The purpose of the present study was to test whether tracer priming given as a flooding dose, thereby securing an instantaneous labeling of the tissue pools of free tracee amino acids, followed by a continuous infusion of the same tracer to maintain tracer isotopic steady state, could be used to determine the MPS rate over a prolonged period of time by obtaining only a single tissue biopsy. We showed that the

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Sparacino, Giovanni, David M. Shames, Paolo Vicini, Janet C. King, and Claudio Cobelli. "Double isotope tracer method for measuring fractional zinc absorption: theoretical analysis." American Journal of Physiology-Endocrinology and Metabolism 282, no. 3 (2002): E679—E687. http://dx.doi.org/10.1152/ajpendo.00113.2001.

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Several approaches for estimation of fractional zinc absorption (FZA) by calculating the ratio of oral to intravenous stable isotopic tracer concentrations (at an appropriate time) in urine or plasma after their simultaneous administration have been proposed in the last decade. These simple-to-implement approaches, often referred to as the double isotopic tracer ratio (DITR) method, are more attractive than the classical “deconvolution” method and the more commonly used single-tracer methods based on fecal monitoring and indicator dilution, after oral or intravenous tracer administration, resp

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Buizert, C., P. Martinerie, V. V. Petrenko, et al. "Gas transport in firn: multiple-tracer characterisation and model intercomparison for NEEM, Northern Greenland." Atmospheric Chemistry and Physics 12, no. 9 (2012): 4259–77. http://dx.doi.org/10.5194/acp-12-4259-2012.

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Abstract. Air was sampled from the porous firn layer at the NEEM site in Northern Greenland. We use an ensemble of ten reference tracers of known atmospheric history to characterise the transport properties of the site. By analysing uncertainties in both data and the reference gas atmospheric histories, we can objectively assign weights to each of the gases used for the depth-diffusivity reconstruction. We define an objective root mean square criterion that is minimised in the model tuning procedure. Each tracer constrains the firn profile differently through its unique atmospheric history and

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Guo, Haihao, Ying Xia, Ruixia Bai, Xingchao Zhang, and Fang Huang. "Experiments on Cu-isotope fractionation between chlorine-bearing fluid and silicate magma: implications for fluid exsolution and porphyry Cu deposits." National Science Review 7, no. 8 (2020): 1319–30. http://dx.doi.org/10.1093/nsr/nwz221.

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Abstract Hydrothermal fluid is essential for transporting metals in the crust and mantle. To explore the potential of Cu isotopes as a tracer of hydrothermal-fluid activity, Cu-isotope fractionation factors between Cl-bearing aqueous fluids and silicate magmas (andesite, dacite, rhyolite dacite, rhyolite and haplogranite) were experimentally calibrated. Fluids containing 1.75–14 wt.% Cl were mixed together with rock powders in Au95Cu5 alloy capsules, which were equilibrated in cold-seal pressure vessels for 5–13 days at 800–850°C and 2 kbar. The elemental and Cu-isotopic compositions of the re

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Sanborn, P. T., R. P. Brockley, and B. Mayer. "Stable isotope tracing of fertilizer sulphur uptake by lodgepole pine: foliar responses." Canadian Journal of Forest Research 41, no. 3 (2011): 493–500. http://dx.doi.org/10.1139/x10-222.

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A plot-scale fertilizer sulphur (S) stable isotope tracer study was established in 2001 in the Sub-Boreal Spruce biogeoclimatic zone in central interior British Columbia where S deficiencies are common in lodgepole pine ( Pinus contorta var. latifolia Engelm. ex S. Wats.) stands. Treatments used operationally realistic applications of 300 kg N·ha–1 as urea and 100 kg S·ha–1 as either sulphate (SO4) or elemental S (S0). δ34S values of fertilizer S differed by >9‰ from pretreatment δ34S values of total S in foliage at the two study sites (5.2‰ and 8.2‰). These differences enabled quantificati

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